Re: [PATCH v1] xen/config.h: Move BITS_PER_* definitions from asm/config.h to xen/config.h

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

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On 3/27/25 1:44 AM, Andrew Cooper wrote:
> On 26/03/2025 5:47 pm, Oleksii Kurochko wrote:
>> diff --git a/xen/include/xen/config.h b/xen/include/xen/config.h
>> index d888b2314d..dbbf2fce62 100644
>> --- a/xen/include/xen/config.h
>> +++ b/xen/include/xen/config.h
>> @@ -98,4 +98,13 @@
>>   #define ZERO_BLOCK_PTR ((void *)-1L)
>>   #endif
>>   
>> +#define BYTES_PER_LONG  __SIZEOF_LONG__
>> +
>> +#define BITS_PER_BYTE   __CHAR_BIT__
>> +#define BITS_PER_INT    (__SIZEOF_INT__ << 3)
>> +#define BITS_PER_LONG   (BYTES_PER_LONG << 3)
>> +#define BITS_PER_LLONG  (__SIZEOF_LONG_LONG__ << 3)
>> +
>> +#define POINTER_ALIGN   __SIZEOF_POINTER__
> See how much nicer this is.  This patch possibly wants to wait until
> I've fixed the compiler checks to update to the new baseline, or we can
> just say that staging is staging and corner case error messages are fine.

Do you mean this patch:https://lore.kernel.org/xen-devel/20250320153241.43809-3-andrew.cooper3@citrix.com/?

I haven't checked clang but if to look at gcc then these builtin macros was introduced in
024a85aeb6a("c-cppbuiltin.c (builtin_define_type_sizeof): New function.") and it seems like even older then gcc5
contains this patch:
$ git tag --contains 024a85aeb6a912811d917f737eaad39140c2fb0c
   ...
   releases/gcc-4.3.0
   ...

Am I missing something?

>
> One thing, you have to replace the "<< 3" as you're hard-coding 8 here
> and ignoring __CHAR_BIT__.
>
> I'd suggest keeping the BITS_PER_BYTE on the LHS, e.g:
>
> #define BITS_PER_INT    (BITS_PER_BYTE * __SIZEOF_INT__)
>
> which tabulates better.

Thanks. I'll update that and send the new patch version.

~ Oleksii

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